1. Field of the Invention
The present invention relates generally to fluid seals, and more particularly to, a fluid seal adapted to be disposed about a cylindrical shaft.
2. Description of the Related Art
Generally, fluid seals are disposed about shafts in motion control dampers, e.g. a piston rod in a shock absorber. Typically, these fluid seals prevent contaminants from entering a housing of the damper while allowing axial movement of the shaft. The fluid seals also retain lubricant within the housing and permit a thin film of lubricant to be disposed on the shaft during movement.
Currently, these dampers may include a gas to aid in dampening. Typically, gas and lubricant are separated within the damper by the fluid seal. As a result, the fluid seal may have one seal portion for the gas and another seal portion for the lubricant along separate paths. An example of such a fluid seal is disclosed in U.S. Pat. No. 4,527,673 to Szcupak. This patented fluid seal includes an elastomeric seal body having a fluid sealing lip which seals against the shaft and a gas sealing lip which seals against a component such as a valve body of the shock absorber to separate a gas retaining portion and a fluid retaining portion. The gas sealing lip also acts as a valve to allow fluid flow in one direction and prevents fluid flow in a reverse direction. For example, under excessive pressure, the gas sealing lip is deflected from the surface of the valve body and fluid may flow between the gas sealing lip and valve body.
One problem with the above patented fluid seal is that the valve body is used as the sealing surface for the valve. Another problem of the patented fluid seal is that the sealing surface must be kept in excellent condition prior to assembly to facilitate proper sealing for the valve. Yet another problem of the patented fluid seal is that the gas sealing lip is lifted from the sealing surface to act as a valve and allow one way fluid flow. A further problem of the patented fluid seal is that the sealing surface for the check valve is made of a rigid material such as steel.